Saturday, June 8, 2013

Root Development of Field Crops

Chimel posted this link in a discussion we had on Raising Organic Matter on Crop Talk. It's a good primer on root development of various crops. This helps me understand why I grow certain crops and when I grow them. Cover crops has greatly modified this root development in soils the past few years. Soybeans were not prominent in the US when the book was written so its root development is not included.

If you read how they did these studies, you can see it was hard, tedious work! I do the same in poor fashion when I can find someone willing to run a backhoe for me. That is usally when I am repairing tile and I can get to the depths the author discusses in this book.

We have been talking about rye this week so let's look at its root development from the book. "Rye (Secale cereale) is an annual and, like winter wheat, makes a good growth when planted in the autumn. Only rarely is it sowed in the spring. Upon germination, it rather regularly produces a whorl of four roots which constitutes the primary root system, thus differing from the other cereals which usually have only three. The mature root system is very similar to that of oats and spring wheat.

Mature Root System.--Plants were grown near Lincoln on rich silt loam soil underlaid with a moist but hard clayey subsoil. The tops at harvest time were 5.5 feet tall and the maximum root penetration was 5 feet. Relatively few roots extended so deeply and the working depth was about 4 feet. Similar depths of penetration were found for Rosen rye growing in an adjacent field, although the tops were 6.5 feet tall. In both cases, the roots were exceedingly well branched to the working depth. In fact, branching is usually better developed in rye than in wheat or oats when growing in the same kind of soil and under the same conditions of moisture. This is one reason why rye is adapted to drier climates than wheat and will thrive on poorer and sandier soils than any of the other cereals. It sometimes produces a fair crop under adverse conditions where other small grains would fail completely. In this connection, the work of Nobbe (1869) is interesting. 147 He compared, measured, and counted the roots of winter wheat and rye plants grown in soil when 55 days old. He found that the roots of the first to the fourth order numbered 16,000 in rye and 10,700 in wheat. The combined lengths of these roots measured 118 and 82 meters, respectively."

Let's contrast that to wheat as I have used both crops heavily to protect and build my soil. "Development of winter wheat under measured environmental conditions has been thoroughly studied at Lincoln, Nebr. 226 A strain of Turkey Red winter wheat (Triticum aestivum), known as Kanred, was grown. It was drilled 2 inches deep in fertile silt loam soil on Sept. 20, and the growth both above and belowground recorded at 10- or 15-day intervals. Growth conditions were very favorable during both years of the experiment, and the crop developed normally.

Early Development.--Ten days after sowing, when the second leaf was about half grown, the roots were excavated (Fig. 64). The number of roots varied from two to five, but nearly all of the plants had three. The primary roots were deepest, extending to maximum depths of 8 to 9 inches. While these roots took a rather vertically downward course, the others usually ran obliquely outward, often later turning downward. The fairly abundant supply of laterals was scattered quite irregularly, the best-branched portions of the root giving rise to 12 or more per inch.

Mature Root System.--At maturity, winter wheat has a very extensive root system. As with other cereals, the abundance of roots, lateral spread, and amount and length of branching, as well as the depth of penetration, are quite variable in different kinds of soil and under different climates. A representative specimen of the Turkey Red variety is shown in Fig. 73. It was grown in moist, rich, silt loam soil near Lincoln. The tops were 3.8 feet high and the heads were well filled. Most of the numerous thread-like roots penetrated rather vertically downward, others ran obliquely downward but seldom reached a greater spread than 6 to 8 inches from the base of the plant. Still others ran out parallel with the soil surface for short distances before turning downward.

The working depth was found at approximately 4.4 feet, and the maximum root depth was 6.2 feet. Beginning just below the surface and extending to a depth of 4 feet, numerous profusely branched laterals filled the soil. These light-colored roots showed very plainly in the black earth. They were covered with dense mats of root hairs, the rootlets intercrossing in the jointed subsoil in such a manner as to give a cobwebby appearance. It is quite impossible to show these finer roots and all their branches in the most detailed drawing. Below 4 feet, the roots were less abundant but still well branched and supplied with root hairs.' The last 6 inches of the deeper ones were poorly branched with laterals which were only a few millimeters in length."

This makes me want to dig up my wheat crop as it fills kernals. What have I done compared to these old studies and how has wheat and rye changed in 75-100 years. Our yields have went up but how has the plant changed to accomplish that? I don't see our soils changing that much and I am just getting them back to where they might have been 50 years ago when they were plowed and rotated.

It's an interesting piece and I struggle to improve yields and profit while trying to improve my native soil after the way its been treated at the same time.